ISPconfig installation broke

Hello again,
I have a serious problem with my installation.
ISPconfig seems to not respond any more. Let me explain. It was working fine. I had it up to date and centos is up to date with yum update. At 23:26 i tried to disable a disable a dns zone, so i went to the ispconfig control panel, at the dns and made a zone inactive but had the feeling that the zone didn't deactivated because i was doing "dig example.com" and return my ip address. I checked /etc/named.conf.local and the zone was there, waited some minutes and desided to restart named. The zone was still there. Deleted the zone and restarted the server but the zone still there. Then i tried adding a new zone but the zone wasn't added. At the ISPConfig it looks like it is added and the one i tried to delete isn't there but it's still in the /etc/named.conf.local file.
Then i checked the monitor of the server and everything looks like to have stopped at 23:25. No logs are read from the monitor after that.
I checked the syslog and the log is working.
At the time of the issue the syslog says:

PHP Fatal error: Call to undefined function posix_getgrnam() in /usr/local/ispconfig/server/plugins-available/shelluser_base_plugin.inc.php on line 165

Click to expand...

The php posix functions seem to be missing in your php binary or you disabled it in php.ini. Please install the php posix functions package from centos if it is not installed and check your php.ini if you disabled it otherwise.

Thank you both very much! It worked and fixed the problem! You saved me from hours of work!
For future reference the problem was that ISPConfig was not writing at the hard disk.
I commented out the server.sh cron job: